[Bug uprobes/10595] New: uprobe return probes causes selinux failures

["mjw at redhat dot com" <sourceware-bugzilla at sourceware dot org>]

When selinux is in enforcing mode and allow_execstack=false trying to set uprobe
return probes on an executable causes selinux denials (and failing to insert the
probe).

Take for example the bz10078.exp testcase, which simply does:

probe process("./bz10078").function("mkpoint*").return {
	printf("%s returns\n", probefunc())
}

With selinux in enforcing mode and disallowing executable stacks:
$ setenforce Enforcing
$ setsebool allow_execstack=false
$ stap systemtap.base/bz10078.stp -c ./bz10078

/var/log/messages:
setroubleshoot: SELinux is preventing bz10078 from changing a writable memory
segment executable. For complete SELinux messages. run sealert -l
725eeb90-824c-4e00-b0c5-3575cdf7d070

$ sealert -l 725eeb90-824c-4e00-b0c5-3575cdf7d070

Summary:

SELinux is preventing bz10078 from changing a writable memory segment
executable.

Detailed Description:

The bz10078 application attempted to change the access protection of memory
(e.g., allocated using malloc). This is a potential security problem.
Applications should not be doing this. Applications are sometimes coded
incorrectly and request this permission. The SELinux Memory Protection Tests
(http://people.redhat.com/drepper/selinux-mem.html) web page explains how to
remove this requirement. If bz10078 does not work and you need it to work, you
can configure SELinux temporarily to allow this access until the application is
fixed. Please file a bug report
(http://bugzilla.redhat.com/bugzilla/enter_bug.cgi) against this package.

Allowing Access:

If you trust bz10078 to run correctly, you can change the context of the
executable to execmem_exec_t. "chcon -t execmem_exec_t '<Unknown>'". You must
also change the default file context files on the system in order to preserve
them even on a full relabel. "semanage fcontext -a -t execmem_exec_t '<Unknown>'"

Fix Command:

chcon -t execmem_exec_t '<Unknown>'

Additional Information:

Source Context                unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1
                              023
Target Context                unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1
                              023
Target Objects                None [ process ]
Source                        bz10078
Source Path                   <Unknown>
Port                          <Unknown>
Host                          springer.wildebeest.org
Source RPM Packages           
Target RPM Packages           
Policy RPM                    selinux-policy-3.6.12-80.fc11
Selinux Enabled               True
Policy Type                   targeted
MLS Enabled                   True
Enforcing Mode                Enforcing
Plugin Name                   allow_execmem
Host Name                     springer.wildebeest.org
Platform                      Linux springer.wildebeest.org
                              2.6.29.6-217.2.16.fc11.x86_64 #1 SMP Mon Aug 24
                              17:17:40 EDT 2009 x86_64 x86_64
Alert Count                   2
First Seen                    Thu Sep  3 14:08:51 2009
Last Seen                     Thu Sep  3 14:10:20 2009
Local ID                      725eeb90-824c-4e00-b0c5-3575cdf7d070
Line Numbers                  

Raw Audit Messages            

node=springer.wildebeest.org type=AVC msg=audit(1251979820.974:270): avc: 
denied  { execmem } for  pid=12251 comm="bz10078"
scontext=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023
tcontext=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 tclass=process

-- 
           Summary: uprobe return probes causes selinux failures
           Product: systemtap
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: uprobes
        AssignedTo: systemtap at sources dot redhat dot com
        ReportedBy: mjw at redhat dot com


http://sourceware.org/bugzilla/show_bug.cgi?id=10595

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